The present invention relates to a vinyl chloride-based polymer (hereinafter referred to as PVC)-polyurethane (hereinafter referred to as PU) composite comprising PU, PVC and plasticizer and having low hardness and excellent hydrolysis resistance, compression set characteristic and profile extrusion moldability, and a method of producing the same.
Japanese Unexamined Patent Publication No. Hei 3-294326 (U.S. Pat. No. 5,360,871) proposed a vinyl chloride-based resin composition wherein vinyl chloride resin, polymer polyol with a specified molecular weight range and compound with three or more isocyanate groups were heated, molten and mixed under shear force and the tetrahydrofuran insolubles of said composition were 5 to 55% by weight.
Japanese Unexamined Patent Publication No. Hei 4-220416 proposed a vinyl chloride-based resin composition with excellent gelling meltability and surface smoothness wherein vinyl chloride-based resin composition obtainable by adding 5 to 100 parts by weight of plasticizer to 100 parts by weight of vinyl chloride resin followed by drying-up, polymer polyol and isocyanate compound with three or more isocyanate groups were heated, molten and mixed under shear force and the tetrahydrofuran insolubles of said composition were 5 to 60% by weight.
Japanese Unexamined Patent Publication No. Hei 6-184384 proposed a method of producing transparent vinyl chloride-polyurethane elastomer wherein PVC, polymer polyol with a specified molecular weight and molecular structure, isocyanate compound with three or more isocyanate groups and plasticizer were heated, molten and mixed under shear force.
Japanese unexamined Patent Publication No. Hei 6-306233 proposed a thermoplastic elastomer resin composition wherein it comprised poly(vinyl chloride)-based resin, polyurethane and plasticizer and it used polyurethane with crosslinking structure as a polyurethane and with a value of loss tangent (tan .delta.) obtainable from the temperature dependence of dynamic viscoelasticity in linear region and tensile mode being 0.3 or higher at a temperature 30.degree. C. higher than the glass transition temperature estimated from the maximum value of tan .delta..
The vinyl chloride-based resin compositions obtainable from Japanese Unexamined Patent Publication No. Hei 3-294326 and Japanese Unexamined Patent Publication No. Hei 4-220416 had high hardness, which was not satisfactory for the requirement of hardness reduction.
The transparent poly(vinyl chloride)-polyurethane elastomer obtainable from Japanese Unexamined Patent Publication No. Hei 6-184384 gave the surface smoothness not always satisfactory on extrusion molding.
The thermoplastic elastomer resin composition obtainable from Japanese Unexamined Patent Publication No. Hei 6-306233 also fell one jump short for the requirement of hardness reduction.
And, these materials obtainable by the methods aforementioned were poor in the profile extrusion moldability, particularly in the case of hardness reduction, because they incurred adhesion to metal on extrusion molding. The purpose of the invention is to provide a PVC-PU composite comprising PVC, PU and plasticizer and having low hardness and excellent hydrolysis resistance, compressive permanent strain characteristic and profile extrusion moldability, and a method of producing the same with high productivity.
In view of the present situation as described above, the inventors contemplated the hardness reduction through the formulation level of polymer polyol (2), molar ratio of NCO/OH, formulation level of plasticizer (4), kneading method and the like, and have found that a PVC-PU composite with improved surface smoothness on extrusion molding and profile extrusion moldability can be obtained through the improvement in kneading method and the finding of suitable processing aid, leading to the completion of the invention.